# Nuclear Science and Techniques

《核技术》(英文版) ISSN 1001-8042 CN 31-1559/TL     2019 Impact factor 1.556

Nuclear Science and Techniques ›› 2018, Vol. 29 ›› Issue (6): 90

### A density functional theory study on the interaction between UO22+ and the carbamoylphosphoramidic acid ligand for uranium extraction from seawater

Xiao-Jing Guo 1 • Cheng Li 1 • Jiang-Tao Hu 1 • Hong-Juan Ma 1 • Hong-Liang Qian 2

1. 1 Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China
2 School of Engineering, China Pharmaceutical University, Nanjing 210009, China
• Contact: Xiao-Jing Guo E-mail:guoxiaojing@sinap.ac.cn
• Supported by:

This work was supported by the National Natural Science Foundation of China (Nos. 21676291, 21406272, 21571185, and 11605273), the Shanghai Sailing Program (No. 16YF1408500), and the Jiangsu Planned Projects for Postdoctoral Research Funds (No. 1402060B).

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Xiao-Jing Guo, Cheng Li, Jiang-Tao Hu, Hong-Juan Ma, Hong-Liang Qian. A density functional theory study on the interaction between UO22+ and the carbamoylphosphoramidic acid ligand for uranium extraction from seawater.Nuclear Science and Techniques, 2018, 29(6): 90
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Abstract:

Phosphorylurea molecules, which contain both phosphoryl and carbonyl groups, are considered efficient extractants for UO22+ . This study aims to explain the complexation of UO22+ with carbamoylphosphoramidic acid (CPO), a simple model for phosphorylurea, for ligand design for uranium recovery from seawater using density functional theory calculations, natural bond order analysis, and the quantum theory of atoms in molecules. The results showed that, when CPO acts as a monodentate ligand, the affinity of phosphoryl for UO22+ is stronger than that of carbonyl, and CPO coordinates with UO22+ through the phosphoryl oxygen atom. When CPO serves as a bidentate ligand, both the phosphoryl and carbonyl oxygen atoms connect to UO22+, and the U–O(carbonyl) bond plays a more important role than the U–O(phosphoryl) bond in the interaction between UO22+ and CPO. This paradox may be caused by the significant charge transfer from the U– O(carbonyl) π bond orbital to the C–N σ antibond orbital of the bidentate CPO. The NH spacer between the phosphoryl and carbonyl groups could ensure the delocalization of the electron system of the molecule. The bidentate binding motif is favored by entropy and opposed by enthalpy, while the monodentate binding motif is favored by enthalpy and opposed by entropy. Ultimately, the bidentate binding motif is more favorable than the monodentate one. As expected, the interaction between UO22+ and the deprotonated CPO is stronger than that between UO22+ and the neutral CPO. Comparing the interaction between UO22+ and CPO with that between UO22+ and Nphenylcarbamoylphosphoramidic acid (PhCPO), formed by replacing one hydrogen atom from the terminal nitrogen atom of CPO with a phenyl group, the phenyl substituent at the terminal nitrogen atom of PhCPO shows a slightly negative effect on the interaction between UO22+ and PhCPO.